I like zombie movies, but even in the suspension of disbelief mode, you don't need to worry about shooting them. all you have to do to escape them is hole yourself up for about a week or two. Zombies eat people, but can they digest them? How long can the undead possibly keep going before they decay too much? All you have to do is lock yourself in for a week with a jug of water and some crackers, and that's it. Not much movie material. Movie's like invasion of the body snatchers have a far better premise.
And how do a bunch of lumbering unarmed dead people overwhelm an Abrams tank? Even assuming they could take out army bases on land, what about the navy? Where are the carrier battlegroups in the middle of the Pacific Ocean? Zombies couldn't touch them!